The invention relates to a method and to an apparatus for producing curved workpieces, the workpiece being shaped in the female die of an extrusion press and leaving the latter in the outlet direction of extrudate.
Curved aluminum profiles are used in different areas of technology, especially in the construction of vehicles running on rails or streets and of aircraft. Conventionally, these workpieces are manufactured by straight extrusion presses with subsequent stretching and bending.
In accordance with a further development of this method, the desired final contour is produced by bending practically simultaneously with the extrusion pressing (EP 0706843 A1). For this purpose, conventional extrusion presses are used, a crosshead usually being employed as a pressure pad with a small opening for supporting the female die.
If the extrusion-molded profile is to be rounded during the bending near the compression mold, the geometry of the press outlets limits the minimum radius, which can be produced. Otherwise, there would be a collision between the extrudate and the press. As a result, the possible product diversity is greatly limited
It is an object of the present invention to make even tighter radii of extruded products possible at little expense and, with that, to expand the spectrum of products, which can be manufactured.
This objective is accomplished by an inventive method owing to the fact that the extruded profile, as it leaves of the female die and before it is bent, is deflected in such a manner, that the outlet direction (A) of the extrudate extends obliquely towards the front, counter to the later curvature of the workpiece. The extrudate, initially emerging from the compression mold obliquely, is aligned so that, due to a subsequent bending towards the other side, it can experience a significantly greater curvature.
In the case of an inventive extrusion molding apparatus for producing curved workpieces with a die holder, in the accommodating opening of which a compression mold package, consisting of a female die with or without a mandrel and a covering part, is disposed, provisions are made so that the guiding surfaces, producing the emerging extrudate, are formed or disposed obliquely by the female die and/or the mandrel corresponding to the extrudate outlet direction, and so that the outlet direction of the extrudate extends at an angle of incidence to the center axis of the female die, counter to the later curvature of the workpiece.
Alternatively, the change in the outlet direction of the extrudate is achieved by
the inclination of the guiding surfaces of the female die and optionally of the mandrel,
the incorporation of a conventional compression mold in a modified die holder and/or by
the incorporation of an oblique, flattened compression mold in a conventional die holder.